Circuit interrupter



OCII. 4, 1966 YOSHlO KOBAYA5| 3,277,407

C IRCUI T INTERRUPTER Filed March 5, 1965 United States Patent C)3,277,407 CIRCUIT INTERRUPTER Yoshio Kobayas, Nara, Japan, assignor toTerasaki Denki Sangyo Kabushiki-Kaisha, Abeno-ku, Osaka,

This invention relates to improvements in a circuit interrupter.

T-he primary object of the invention is to provide an improved circuitinterrupter, in addition to being brought into its stable open statethrough the operation of the conventional thermally orelectromagnetically operated tripping device, capable of opening theassociated circuit without any delay upon the occurrence of a llow ofheavy current such as a shortcircuiting current and a little later,being maintained in its stable open state through the operation of suchtripping device.

With this object in view, the invention resides in a circuit interruptercomprising a pair of movable contact arms having disposed on theextremities thereof a pair of contacts respectively and disposed insubstantially parallel relationship in the closed state in which thecontacts engage each other, the pair of movable contact arms beingarranged such that, upon the occurrence of la ow of heavy current suchas shortcircuiting current, one of the movable contact arms isimmediately moved away from the other contact arm `under the action ofan electromagnetic repulsion generated between the parallel disposedcontact arms due to the ow of heavy current therethrough thereby to bebrought into its open position while at a little later, the othercontact arm constrained in its closed position by a switching mechanismis moved to be separated far away from the one contact arm throughcollapsing of the switching mechanism due to the operation of athermally or electromagvnetically tripping mechanism, and a springmember for providing a contact pressure for the contacts and returningthe one contact arm to its original position as the electromagneticrepulsion decreases.

The invention will become more readily apparent from the followingdetailed description taken 4in conjunction with the accompanyingdrawings in which:

FIG. l shows, partly in section and partly in elevation, a circuitinterrupter constructed in accordance with the teachings of theinvention;

FIG. 2 is a fragmental elevational view of a pair of movable contactarms and their associated components in their ON and OFF positions; and

FIG. 3 is a view similar to FIG. 2 but illustrating the contact arms intheir tripped position.

While the invention' will be shown and described in conjunction with acircuit interrupter of three pole type, it is to be understood that thesame is equally applicable to circuit interrupters of single pole typeand other multiple pole types. Also it is to be understood that thecomponents common to all the poles will be described in terms of thecentral pole alone.

Referring now to the drawings and more particularly to FIG. 1, there isillustrated a three pole circuit interrupter constructed in laccordancewith the teachings of the invention. The circuit interrupter illustratedcomprises a base member 1 and a detachable cover plate 2. The Ibasemember 1 and the cover plate 2 may be conveniently made of any suitableelectrically insulating plastic by the molding technique and constitutea closed enclosure. Within the enclosure a pair of movable contact arms3 and 4 are disposed so as to be substantially horizontally positionedin parallel relationship .in the closed position of the inter- 3,277,407Patented Oct. 4, 1966 rupter. The contact arms 3 and 4 are made of anysuitable electrically conductive material and have a pair of contcts 3aand 4a attached at their free ends respectively.

The lower contact arm 4 is pivotally mounted on a rotatable shaft 7 by aU-shaped support Imember 8 for rotation about the shaft 7. Disposed oneither common side of the lower contact arm 4 and U-shaped supportmember 8 is a helical spring 9 having one end hooked to a pin 10extending through the contact arm and the other end secured to a pin 11disposed on the U-shaped support member. The spring 9 serves -to provideto the lower contact on the lower Contact arm 4 a pressure under whichthe contact 4a engages the upper contact 3a. The lower contact arm 4 hasthe other end connected by way of a flexible conductor 12 to a conductor13 connected to a source terminal 14.

The lupper contact arm 3 is rotatably secured to a contact holder 15pivotally mounted on a holder shaft 16 common to all `the poles and alsois connected to a connector 17 through a llexible conductor 18.

In order to prevent any effective shortcircuiting between the opposingportions of the upper and lower contact arms 3 and 4 in their closedpositions or in parallel relationship, a thin insulation 5 is interposedtherebetween.

In order to manually move the upper movable contact arm 3 from itsclosed position as illustrated at solid line in FIG. 2 to its openposition as illustrated at dot-and-dash line in FIG. 2 and at solid linein FIG. 3 and vice versa, an operating mechanism generally designated bythe reference numeral 20 is provided including an operating handle 21,an operating spring 22 and a tripping plate 23. The tripping plate 23 isthen operatively connected to the contact holder 15 through a pair oftoggle levers 24.

The interrupter also further comprises a thermally responsive devicegenerally designated by the reference numeral 25 for the purpose oftripping the interrupter upon the occurrence of a flow of ordinaryoverload current. The thermally responsive device 25 includes a bimetalelement 26 electrically connected to the connector 17 through aconductor 27 and an electric resistor 28 of U- shaped disposed Iadjacentthe bimetal element 27. The resistor 28 has one end connected to theconductor 27 and the other end connected to another conductor 29 which,in turn, is connected to a load terminal 30. As shown in FIG. l, anadjusting screw 31 is secured integrally at the free end of the bimetalelement 26. Upon the occurrence of a ilow of ordinary overload current,the resistor 28 and hence the bimetal element 26 will be heated wherebythe element is bent leftwardly as viewed in FIG. l to actuate a trippingmechanism which will be subsequently described.

The tripping mechanism generally designated by the 'reference numeral 32includes -a tripping piece 33. Upon the occurrence of a ow of ordinaryoverload current, the tripping piece 33 is forced by the adjusting screw31 to rotate a tripping rod 34 integral with the tripping piece and ashaft 35 for the tripping rod whereby a tripping cam 36 disengages from`a tripping hook 37 mounted on the tripping rod 34 resulting in atripping operation.

If an excessive current whose magnitude may be in the order of 8 to 10times the ratin-g current flows through the interrupter then anelectromagnet device including a stationary iron core 38 and a movableiron core 39 is energized to perform an instaneously tripping operation.More specifically, the lstationary iron core 3S is excited with acurrent flowing through the conductor 27 to attract the movable ironcore 39 thereby to rotate the tripping rod 34 to disengage the trippingcam 36 from the tripping hook 37 resulting in a tripping operation.

With the arrangement thus far described, a How of overload current owingthrough the interrupter in its closed position causes energization ofboth the thermally responsive device 25 and the electromagnet device38-39 thereby to trip the circuit interrupter. That is, the upperImovable contact arm 3 is released from its constrained state to rotatein the clockwise direction until the same reaches its position asillustrated at dot-and-dash line in FIG. 2 and at a solid line in FIG.3. This completes the tripping operation.

However, if a very high current such as a shortcircuiting current flowsthe circuit interrupter then such current will flow through the upperand lower contact arms 3 and 4 disposed in parallel, in the oppositedirections, which generates an electromagnetic repulsion between bothcontact arms. This electromagnetic repulsion does not aect the uppercontact arm 3 because the latter is constrained in its closed positionby the switching or operating mechanism 20 but is effective for drivingthe lower contact arm 4 having a contact pressure applied thereto by thespring 9 and tending to rotate the arm 4 in the clockwise direction.about the shaft 7. Therefore, magnetic repulsion causes rotationalmovement of the lower contact arm 4 and accordingly the lower contact 4aagainst the contact pressure just described with the result that thelower contact arm 4 is separated away from the upper contact arm 3 andhence the upper contact 3a resulting in the interrupter beinginterrupted,

Thus the lower contact arm 4 has now been separated from the uppercontact arm 3 thereby to interrupt the very high current. A littlelater, the electromagnetically tripping device 38-39 is operated tooverride the ability of the switchin-g mechanism 2-0 to constrain theupper contact arm 3 thereby to rotate the upper contact arm 3 in theclockwise direction as viewed in FIG. 2 to be further separated awayfrom the lower contact arm 4 until the same is brought into its openposition as illustrated at s-olid line in FIG. 3. Immediately before orafter the upper contact arm 3 has been brought into its open positionthe electromagnetic repulsion as previously is damped to be lower thanthe force of the spring 9 tending to rotate the lower `contact arm 4clockwise whereupon the arm 4 returns back to its original position asillustrated at solid line in FIG. 3.

If it is then desired to close the interrupter, a resetting operationleads to the interrupter being ready for closing state.

From the foregoing it will be appreciated that due to the provision of apair of movable contact arms 3 and 4 disposed in substantially parallelrelationship in their closed positions a flow of heavy current such asshortcircuiting current generates an electromagnetic repulsion betweenboth contact arms thereby to separate one of the movable contact armsaway from the other contact arm without any delay while the othercontact arm remains stationary by the action of the switching mechanismwith the result that the associate circuit is interrupted within a veryshort period of time. This causes the current limiting eiect and theinterruption capacity of the interrupter to increase. A little later`after this interruption, the thermally responsive and/ orelectromagnetic tripping mechanisms of the conventional type are or isoperated to put the other contact arm in its open position. Then as theelectromagnetic repulsion decreases the one contact `arm returns back toits original position by the action of the associated spring resultingin the readiness for the subsequent closing operation.

What I claim is:

1. A circuit interrupter consisting essentially of a pair of movable.contact arms having opposed contacts at their respective extremitiesand disposed in substantially sideby-side parallel relationship in theclosed state in which the contacts engage each other, so that thecurrent flow in one arm is in the opposite direction to the current owin the other arm, switching means coupled to one of said arms fordriving said one arm from its closed position to its open position andvice versa, release means coupled to said one arm for -moving said onearm lfor causing automatic separation of said one movable contact armfrom the other, thermally responsive and electromagnetic trip meansresponsive to a ow of overload current through the circuit interrupterand engageable with said release means to a-ctuate said release means, asupport member having the other movable contact arm pivotably mountedthereon and rotatable about a pivot on said support member independentof the operation of said switching means, said releasable means and saidthermally responsive and electromagnetic trip means, a spring memberextending between said other movable contact arm and said support memberand biasing said other movable contact arm toward its closed positionwhereby when a short circuiting current flows through said pair ofmovable contact arms in the opposite direction causing temporaryseparation of said other movable contact -arm from said one movablecontact arm due to electromagnetic repulsion, a time is provided duringwhich said electromagnetic trip means can respond tothe current, saidone movable contact arm controlled by said switching means is moved toits open position through the operation of said switching meansresulting from said response of said electromagnetic trip meanswhereupon the interruption operation is made permanent and the othermovable contact arm is automatically returned to its original positionas the electromagnetic repulsion decreases 2. A'circuit interrupter asclaimed in claim 1 in which said spring member acts along a line betweensaid other movable contact and said pin, and is suiciently strong toprevent pivoting of the said other contact arm far enough so that thespring is moved past its dead center position.

References Cited by the Examiner UNITED STATES PATENTS 2,932,706 4/ 1960Bodenschatz 200-107 3,005,073 10/ 1961 Reiss et al. 200-94 3,127,488 3/1964 Bodenschatz 200-106 BERNARD A. GILHEANY, Primary Examiner. I. J,BAKER, Assistant Examiner,

1. A CIRCUIT INTERRUPTER CONSISTING ESSENTIALLY OF A PAIR OF MOVABLECONTACT ARMS HAVING OPPOSED CONTACTS AT THEIR RESPECTIVE EXTREMITIES ANDDISPOSED IN SUBSTANTIALLY SIDEBY-SIDE PARALLEL RELATIONSHIP IN THECLOSED STATE IN WHICH THE CONTACTS ENGAGE EACH OTHER, SO THAT THECURRENT FLOW IN ONE ARM IS IN THE OPPOSITE DIRECTION TO THE CURRENT FLOWIN THE OTHER ARM, SWITCHING MEANS COUPLED TO ONE OF SAID ARMS FORDRIVING SAID ONE ARM FROM ITS CLOSED POSITION TO ITS OPEN POSITION ANDVICE VERSA, RELEASE MEANS COUPLED TO SAID ONE ARM FOR MOVING SAID ONEARM FOR CAUSING AUTOMATIC SEPARATION OF SAID ONE MOVABLE CONTACT ARMFROM THE OTHER, THERMALLY RESPONSIVE AND ELECTROMAGNETIC TRIP MEANSRESPONSIVE TO A FLOW OF OVERLOAD CURRENT THROUGH THE CIRCUIT INTERRUPTERAND ENGAGEABLE WITH SAID RELEASE MEANS TO ACTUATE SAID RELEASE MEANS, ASUPPORT MEMBER HAVING THE OTHER MOVABLE CONTACT ARM PIVOTABLY MOUNTEDTHEREON AND ROTATABLE ABOUT A PIVOT ON SAID SUPPORT MEMBER INDEPENDENTOF THE OPERATION OF SAID SWITCHING MEANS, SAID RELEASABLE MEANS AND SAIDTHERMALLY RESPONSIVE AND ELECTROMAGNETIC TRIP MEANS, A SPRING MEMBEREXTENDING BETWEEN SAID OTHER MOVABLE CONTACT ARM AND SAID SUPPORT MEMBERAND BIASING SAID OTHER MOVABLE CONTACT ARM TOWARD ITS CLOSED POSITIONWHEREBY WHEN A SHORT CIRCUITING CURRENT FLOWS THROUGH SAID PAIR OFMOVABLE CONTACT ARM; IN THE OPPOSITE DIRECTION CAUSING TEMPORARYSEPARATION OF SAID OTHER MOVABLE CONTACT ARM FROM SAID ONE MOVABLECONTACT ARM DUE TO ELECTROMAGNETIC REPULSION, A TIME IS PROVIDED DURINGWHICH SAID ELECTROMAGNETIC TRIP MEANS CAN RESPOND TO THE CURRENT, SAIDONE MOVABLE CONTACT ARM CONTROLLED BY SAID SWITCHING MEANS IS MOVED TOITS OPEN POSITION THROUGH THE OPERATION OF SAID SWITCHING MEANSRESULTING FROM SAID RESPONSE OF SAID ELECTROMAGNETIC TRIP MEANSWHEREUPON THE INTERRUPTION OPERATION IS MADE PERMANENT AND THE OTHERMOVABLE CONTACT ARM IS AUTOMATICALLY RETURNED TO ITS ORIGINAL POSITIONAS THE ELECTROMAGNETIC REPULSION DECREASES.